Process of reclaiming foundry sand



Aug. 10, 1943. w. HARTLEY ETAL PROCESS OF RECLAIMING FOUNDRY SAND Filed Aug. 30, 1941 Patented Aug. 10, 1943 PROCESS F RECLAIM'ING FOUNDRY SAND William L. Hartley, Chicago, Ill., and Donald Whitehead, Wyoming, Ohio, assignors to Link- Belt Company, a. corporation of Illinois Application August 30, 1941, Serial No. 408,950

Claims.

Our invention relates to apparatus for and process of reclaiming foundry sand. It has for one object to provide a new and improved means for retreating, renovating and reclaiming foundry sand and especially core sand so that it may be reused.

Core sand or sand used in making dry sand cores, as distinguished from molding sand for metal casting and the like is ordinarily a fine grade of silica sand, it is mixed with linseed oil or other suitable materials and binders which is thcn formed in core molds or core lboxes, and is finally baked or dried and the resultant core is used as part of the mold for casting.

After the casting has been taken out of the mold, the core is removed from the casting by jarring, rattling or other suitable treatment and the used core sand has, in the past, generally been discarded or thrown away. The reason for this waste of the used core sand in the past 1s that the carbonaceous or other material adhering to the sand grains makes it impractical to use that sand again because only clean sand can successfully be used in the manufacture of suitable cores.

Many efforts in the past have been made to clean or reclaim used core sand for reuse by chemical treatment,vwashing, abrading, etc. all without practical success. We have discovered that if the used core sand or molding sand is heated to within the range of 500 to 1800 degrees F., all but a small proportion of it can be reused because by such heat treatment the burnt and spent binders and the foreign matter adhering to the sand grains will be removed by burning or vaporizing as the case may be and the resultant reclaimed sand will be reconditioned for reuse for making cores or for molding sand in place of new sand.

` Other objects will appear from time to time throughout the specification and claims.

Our invention is illustrated more or less diagrammatically in the accompanying drawing, Wherein- Figure 1 is a side elevation of a core sand recovery plant;

Figure 2 is a .plan view with parts omitted;

Figure 3 is an end view on a larger scale.

Like parts are indicated by like characters throughout the specification and drawing.

I is an elevated platform. It carries a surge hopper 2, having a mechanical feeder 3, feeding through a packing or choke feed passage 4 into the stack 5, or directly into a rotary kiln 6. The kiln is the usual type of inclined rotary kiln having track rings 'I riding on rollers 8 on pedestals 9 supported on a frame I0, the frame I0 and the platform I, being supported by the uprights II.

I2 is a driving gear in mesh with a pinion I3 driven through reducing gears by a motor I4 to rotate the kiln. I5 is a burner housing mounted on rollers I6 or may be suspended from overhead rollers adapted to travel along the frame I0 and containing any suitable burner nozzles 5 or jets not here shown. This housing may be moved into position to enclose the lower end of the kiln during operation or may be withdrawn away from the end of the kiln to permit access thereto. 10 Used molding or core sand supplied tothe surge hopper 2 by any suitable means is fed by the screw or other suitable feeder 3 through the seal 4 into the stack, passes through the kiln and is discharged throughD the chute I1 into a cooler I8. This cooler I8 has track rings I9 engaging rollers on bases 2|, is driven by the gear 22, pinions 23, motor 24. The cooler is preferably a louvre type wherein air is discharged into the space within the cylinder housing, passes 20 through the louvres lining the housing and so IpasSes through the material in the cooler, the

material being thus subjected to the air blast as it passes through the rotating cooler. The sand passes through the cooler, discharges into an air exhaust chamber where fines in suspension will be carried olf with exhaust air therefrom and the reclaimed sand is discharged onto a belt or other type of conveyor.

28 is an inlet fan delivering cooling air 30 through a boot 29 into the outer periphery of the cooler I8. The air passes through the material in the cooler, is discharged into the exhaust hood 30, passes up through a conduit 3| to a dust collector 32, the collected dust being discharged from the system at 33, the spent air passing. out through a conduit 34, exhaust fan 35 to the exhaust stack 36.

3l diagrammatically indicates a crusher mounted on the surge hopper 2, adapted to receive the spent core or molding sand from a chute 38. Under some circumstances the crusher is not needed becausethe heat applied to the core sand in the kiln is suilicient with the agitation resultant from the rotation of the kiln to break -up the lumps so that fine clean sand is discharged from the kiln to the cooler.

I n order to properly mix and prepare core sand, it should preferably be at a temperature not exceeding 100 degrees F., because for higher temperatures the binders used tends to thin out and their surface tension drops to such a point that adequate coating of the sand grainswill not result and cores of suflicient strength cannot be 55 made.

Since it is necessary to cool the sand, after it is discharged from the kiln, -to a temperature suitable for re-useand since sand in storage retains heat for a long time, the cost of excessive storage facilities needed for natural cooling and special .sand handling equipment can be saved if the sand is cooled before it is placed in storage.

Most of the core sand removed from castings is useable after reconditioning except a certain proportion of the sand, generally that which was in relatively close contact with the molten metal which has been reduced or disintegrated into dust or powder by the heat of the metal. 'I'his .dust or powder must be removed from the reclaimed sand as it will otherwise weaken the core. The

cooler as well as cooling the sand accomplishes sand is discharged through the screenl to the conveyor 26.

It may sometimes happen that even after the heat treatment, there may be a residue of foreign matter left adhering to the sand grains which is not completely expelled by the heat. As the sand passes through the heating zone and the cooling zone and over the vibratinglscreen, if it is used, the abrading, comminuting effect of the handling and movement of the sand will tend to remove such adhering material so that the air blast may withdraw it from the system.

By reference to the surge hopper 2, we mean any suitable hopper which will be of such capacity that as material is fed to it through the chute 38 at sometimes variable rates of speed, the variation in feed will be absorbed by the quantity of material in the hopper sox that the pressure of material on the bottom of the hopper will be sufllciently uniform yto insure. a uniform, constant feed into the apparatus. It is, of course, desired that the feed be as near, to uniform as possible and the surge hopper brings that about.

1. The method of recovering used foundry core sand, which includes moving the used core sand to and through a. heating and oxidizing zone; there subjecting the sand to a temperature high enough to remove adherent carbonaceous and other materials from the sand grains but not high enough to change the grain structure of the sand; thereafter delivering the heated sand to a cooling container; rotating said container and thereby maintaining a movement of the sand within the container, and delivering through the sand, while in the rotating container, a volume of cooling air at suiilcient velocity to suspend the nes therein; delivering the cooled sand and the air from the rotating container into an enclosed chamber; exhausting the air and the nes therein, from said chamber; and conveying the reclaimed sand therefrom for storage or use.

2. An apparatus for recovering used core sand, which includes a rotary kiln, means for delivering the sand to be treated to one end of the kiln, means for rotating the kiln; means for heating the sand in the kiln to a temperature high enough to remove adherent carbonaceous and other materials from the sand grains but not high enough to change the grain structure of the sand, a rotary cooling container and means for rotating it, means for delivering heated sand from the discharge end of the kiln to the rotary cooling container, means for delivering cooling air to the cooling container -and for passing such air from said settling chamber, and means for conveying the cooled reclaimed sand to a point of storage or use.

3. The method of recovering used foundry core sand, which includes moving the used core sand to a heating and oxidizing zone; there subjecting the sand to a temperature high enough to remove adherent carbonaceous and other materials from the sand grains but not highenough to change f the grain structure of the sand; thereafter delivering the heated sand to a cooling chamber; imparting movement to the sand while in said cooling chamber, passing cooling air through the sand, while in motion in said cooling chamber at a velocity suihcient to suspend thefines therein, along a path or paths at an angle to the direction of movement of the sand in the cooling chamber, delivering the cooled sand and the air from the cooling chamber into a settling chamber; drawing oif the air and nes from the settling chamber; and conveying the reclaimed sand to a zone of storage or use.

4. An apparatus for recoverngused core sand, which includes a rotary kiln, means for delivering the sand to be treated to one end of the kiln, means for rotating the kiln; means for heating the sand in the kiln to a temperature4 high enough to remove adherent carbonaceous and other materials from the sand grains but not high enough to change the grain structure of the sand, a rotary cooling container and means for rotating it, means for. delivering heated sand from the discharge end of the kiln to the rotary cooling container, means for delivering cooling air `to the cooling container and for passing such air through the sand in the cooling container at suilicient velocity to suspend the fines therein, a settling chamber and means for delivering thereto the air and the cooled sand from the cooling container, means for maintaining movement of the air in said settling chamber at a velocity less than that of the air passing through the ,cooling container, and for drawing off the air and fines from said settling chamber, and means for conveying the cooled reclaimed sand to a point of storage or use.

5. The method of recovering used foundry core sand, which includes moving the used core sand to and through a rotary kiln; there subjecting the sand to oxidizing conditions at a temperature high enough to remove adherent carbonaceous and other materials from the sand grains but not high enough to change the grain structure of the sand, by passing heated gases of' combustion through the kiln in a direction opposite to the direction of movement of the sand through the kiln, thereafter delivering the heated sand to a cooling container; rotating said container and thereby maintaining a movement of the mass of sand within the container, and delivering through the sand, While in the rotating container, a volume of cooling air at sufficient velocity to suspend the fines therein;l delivering the cooled sand and the air from the rotating container into an enclosed chamber; exhausting the air and the fines therein, from said chamber; and conveying the reclaimed sand therefrom for storage or use.

WILLIAM L. HAR'ILEY. DONALD WHITEHEAD.' 

